Technical Field
The present disclosure relates to an epoxy matrix formulation, an epoxy matrix prepreg, an epoxy matrix composite and a method for manufacturing the thermoplastic epoxy matrix prepreg. More particularly, the present disclosure relates to a thermoplastic epoxy matrix formulation, a thermoplastic epoxy matrix prepreg, a thermoplastic epoxy matrix composite and a method for manufacturing the thermoplastic epoxy matrix prepreg.
Description of Related Art
With the vigorous development of science and technology, composite materials have become the mainstream of modern industry. The composite materials refer to a multiphase solid material composed of at least two substances having different physical and chemical properties. The composite materials generally include a continuous phase and a dispersed phase, wherein the continuous phase is called base material, and the dispersed phase is called reinforcing material. The composite materials are featured with high strength, low density, high acid and alkali resistance and high environmental durability by drawing upon and benefiting from the substances composed thereof or the synergistic effects provided by the substances composed thereof. Accordingly, the composite materials are regarded as a promising material and are gradually replacing conventional metal materials and ceramic materials. The composite materials are widely applied to a variety of fields, such as the field of aerospace industry, transport, sports equipment, building equipment and national defense.
When the base material of the composite materials is made of polymer matrix, the composite materials are called polymer matrix composites. Epoxy resins are widely used to prepare the base material (epoxy matrix), and the polymer matrix composite having the epoxy matrix is called epoxy matrix composite. However, the conventional epoxy matrix made of the epoxy resins is thermoset, which cannot be reshaped after cured. Accordingly, the conventional epoxy matrix composite is thermoset and cannot be recycled after cured, which is not favorable for the subsequent processes and maintenance, and is not environment friendly.
A thermoplastic epoxy matrix composite is provided for addressing the shortcomings of the conventional thermoset epoxy matrix composite. The thermoplastic epoxy matrix of the thermoplastic epoxy matrix composite is polymerized by a difunctional epoxy resin and a difunctional amine hardener, and is inherited most of the advantages of the thermoset epoxy matrix, such as high strength, high rigidity and excellent combining property which is favorable to combine with other material. Furthermore, the thermoplastic epoxy matrix composite is thermoplastic and can be reshaped after fully cured.
However, the potential problem for the thermoplastic epoxy matrix composite is the preparation of a prepreg thereof. The common method for preparing the prepreg includes a melt impregnation process (also known as hot-melt method) and a solution impregnation process. The melt impregnation process includes a mixing stage and an impregnating stage. Specifically, in the mixing stage, the epoxy resin with epoxide groups and a hardener are mixed to form a resin mixture. In the impregnating stage, the resin mixture is contacted with a reinforcing material (such as fibers) for a time, then a resin film combined with the fibers is formed so as to obtain the prepreg. The solution impregnation process is conducted as follows. First, the epoxy resin and the hardener are completely dissolved in a solvent to form a resin solution, then the reinforcing material is contacted with the resin solution for impregnating. Afterwards, the solvent is evaporated so as to obtain the prepreg. Comparing the melt impregnation process to the solution impregnation process, the solvent is not necessary in the melt impregnation process, so that the environmental pollution and the cost can be reduced. Furthermore, the quality of the prepreg and the production efficiency can be enhanced. Accordingly, the melt impregnation process is favored by the relevant industries. However, the temperature required by a thermoplastic epoxy matrix in the mixing stage is about 200° C. to 400° C., which is much higher than that of a thermoset epoxy matrix (the temperature required by the thermoset epoxy matrix in the mixing stage is about 50° C. to 80° C.). Accordingly, the melt impregnation process of the thermoplastic epoxy matrix is energy-consuming. Furthermore, when the epoxy matrix is thermoplastic, the viscosity of the resin mixture increases sharply in the mixing stage due to the heating temperature. As a result, the uniformity of the thickness of the resin film is affected, i.e., the resin content (RC) cannot be precisely controlled. Even more, the excessive viscosity tends to cause the resin mixture to adhere tightly to the inner wall of the resin bath, and the resin bath is difficult to be cleaned.
Therefore, how to improve the formulation of the thermoplastic epoxy matrix, which can reduce the temperature and prevent an excessive viscosity of the resin mixture when preparing the prepreg, and the prepreg can be cured at a higher temperature (about 160° C. to 180° C.) to form the thermoplastic epoxy matrix composite, is the goal of the related industries.